Radiation therapy is already widely known in the prior art. It finds application principally in the treatment of cancerous diseases, whereby accelerated particles are emitted in a targeted manner in such a way that they deposit the majority of their energy in an irradiation target, in particular a tumor. In most cases linear accelerators, often referred to also in abbreviated form as LINACs, are employed for this purpose. What is essential in this context is optimally precise planning of the irradiation that is to be carried out, since it is aimed to strike the actual irradiation target, in particular a tumor, with the utmost precision and to spare healthy tissue as far as possible. In this regard imaging modalities such as computed tomography or magnetic resonance can be used, for example, for irradiation planning purposes. A three-dimensional image dataset of the body region that is to be irradiated, i.e. of the target region containing the irradiation target, is acquired and a unique reference established to the outer shell (surface) of the patient by means of markers or stereotactic frames.
In this regard there exist target regions within the patient, in particular organs, which are subject to displacements inside the body, in the range of several centimeters for example. Examples of this are the lung, which is moved by regular respiration, and the prostate, which can likewise be displaced in the centimeter range due to involuntary intestinal motions. This is why in practice irradiations, of the prostate for example, are performed with a considerable safety margin, which results in substantially the entire organ being irradiated, which can lead to undesirable side effects.
In order to solve this problem it has been proposed to use combination devices in which an image acquisition device, for example a computed tomography device, a magnetic resonance device or an X-ray fluoroscopy system, is combined with an irradiation device, in particular comprising a LINAC. The idea informing the systems proposed here is as complete an integration as possible so that the image acquisition device continuously acquires image data of the target region such that a current position of the irradiation target can be determined and used to control the beam of the irradiation device in such a way that the irradiation target is bombarded to maximum effect, in other words with an optimal dose.
In particular irradiation devices in which an X-ray fluoroscopy system (X-ray device) is already integrated are known in this context. For example, a radiation source whose X-ray beams are received by an oppositely arranged detector can be provided adjacent to a beam exit of the LINAC. On the other hand, soft tissue resolution in particular and also three-dimensional imaging capability are severely limited in the case of X-ray devices, with the result that combination systems composed of magnetic resonance devices and irradiation devices including a linear accelerator have also been proposed. Radiotherapy treatment devices in which a magnetic resonance device and an irradiation device have been integrated with one another are known for example from WO 2003/008986, US 2005/0197564, U.S. Pat. No. 6,366,798, U.S. Pat. No. 6,198,957, DE 10 2008 007 245, DE 10 2010 001 746, DE 10 2007 054 324 and DE 10 2006 059 707. The solutions described in each of the cited publications necessitate large-scale changes to the magnetic resonance configuration and are accompanied by limitations in terms of image quality and enormous costs for the radiotherapy treatment device. Consequently the performance of the devices, the range of applications and patient comfort are frequently severely restricted. What is advantageous about these systems, however, is that often it is no longer necessary to move the precisely positioned patient.